U.S. patent application number 15/773528 was filed with the patent office on 2018-11-08 for base station, terminal and communication method.
The applicant listed for this patent is Panasonic Intellectual Property Corporation of America. Invention is credited to Ayako Horiuchi, Hidetoshi Suzuki.
Application Number | 20180324841 15/773528 |
Document ID | / |
Family ID | 58663140 |
Filed Date | 2018-11-08 |
United States Patent
Application |
20180324841 |
Kind Code |
A1 |
Horiuchi; Ayako ; et
al. |
November 8, 2018 |
BASE STATION, TERMINAL AND COMMUNICATION METHOD
Abstract
A signal assignment unit (105) assigns a downlink control signal
including resource assignment information of a PDSCH to a downlink
resource. A specification unit (108) specifies a PUCCH resource
using an offset value set to either a first PRB set or a second PRB
set when the downlink control signal is disposed to spread over the
first PRB set and the second PRB set. A signal separation unit
(109) separates an ACK/NACK signal included in the specified PUCCH
resource from a received signal from a terminal to which the
downlink control signal has been transmitted.
Inventors: |
Horiuchi; Ayako; (Kanagawa,
JP) ; Suzuki; Hidetoshi; (Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Intellectual Property Corporation of America |
Torrance |
CA |
US |
|
|
Family ID: |
58663140 |
Appl. No.: |
15/773528 |
Filed: |
September 12, 2016 |
PCT Filed: |
September 12, 2016 |
PCT NO: |
PCT/JP2016/004130 |
371 Date: |
May 3, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/04 20130101;
H04L 5/0055 20130101; H04L 1/16 20130101; H04W 72/1289 20130101;
H04W 88/08 20130101; H04W 72/12 20130101 |
International
Class: |
H04W 72/12 20060101
H04W072/12; H04L 1/16 20060101 H04L001/16 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 6, 2015 |
JP |
2015-218437 |
Claims
1. A base station comprising: a signal assignment section that
assigns a downlink control signal to a downlink resource, the
downlink control signal including resource allocation information
on Physical Downlink Shared Channel (PDSCH); an identifying section
that identifies a Physical Uplink Control Channel (PUCCH) resource
based on the downlink resource to which the downlink control signal
has been assigned, the PUCCH resource being a resource to which an
ACK/NACK signal for the PDSCH is assigned; and a signal separating
section that separates the ACK/NACK signal included in the
identified PUCCH resource from a received signal from a terminal to
which the downlink control signal has been transmitted, wherein the
downlink resource is composed of a plurality of PRB pairs, and any
of a first PRB set and a second PRB set is assigned to each of the
plurality of PRB pairs, and in a case where the downlink control
signal is mapped over the first PRB set and the second PRB set, the
identifying section identifies the PUCCH resource, using an offset
value configured for any of the first PRB set and the second PRB
set.
2. The base station according to claim 1, wherein mutually
different offset values are configured for the first PRB set and
the second PRB set, respectively, and in a case where the downlink
control signal is mapped over the first PRB set and the second PRB
set, the identifying section identifies the PUCCH resource, using
an offset value configured for a PRB set assigned to a PRB pair
having a minimum PRB number, among the first PRB set and the second
PRB set.
3. The base station according to claim 1, wherein mutually
different offset values are configured for the first PRB set and
the second PRB set, respectively, and in a case where the downlink
control signal is mapped over the first PRB set and the second PRB
set, the identifying section identifies the PUCCH resource, using
an offset value configured for a PRB set having a smaller PRB set
number among the first PRB set and the second PRB set.
4. The base station according to claim 1, wherein mutually
different offset values are configured for the first PRB set and
the second PRB set, respectively, and in a case where the downlink
control signal is mapped over the first PRB set and the second PRB
set, the identifying section identifies the PUCCH resource, using
an offset value having a smaller value among the offset values
configured for the first PRB set and the second PRB set.
5. The base station according to claim 1, wherein a common offset
value is configured for the first PRB set and the second PRB set,
and the identifying section identifies the PUCCH resource, using
the common offset value.
6. The base station according to claim 1, wherein mutually
different offset values are configured for the first PRB set and
the second PRB set, respectively, and in a case where the downlink
control signal is mapped over the first PRB set and the second PRB
set, the identifying section identifies the PUCCH resource, using
an offset value configured for a PRB set in which the downlink
control signal is mapped first, among the first PRB set and the
second PRB set.
7. The base station according to claim 6, wherein the number of PRB
pairs to which the PRB set in which the downlink control signal is
mapped first is assigned is greater than the number of PRB pairs to
which a PRB set in which the downlink control signal is mapped
later is assigned.
8. A terminal comprising: a receiving section that receives a
downlink control signal including resource allocation information
on Physical Downlink Shared Channel (PDSCH); an identifying section
that identifies a Physical Uplink Control Channel (PUCCH) resource
based on a downlink resource to which the downlink control signal
has been assigned, the PUCCH resource being a resource to which an
ACK/NACK signal for the PDSCH is assigned; and a signal assignment
section that assigns the ACK/NACK signal to the identified PUCCH
resource, wherein the downlink resource is composed of a plurality
of PRB pairs, and any of a first PRB set and a second PRB set is
assigned to each of the plurality of PRB pairs, and in a case where
the downlink control signal is mapped over the first PRB set and
the second PRB set, the identifying section identifies the PUCCH
resource, using an offset value configured for any of the first PRB
set and the second PRB set.
9. A communication method comprising: assigning a downlink control
signal to a downlink resource, the downlink control signal
including resource allocation information on Physical Downlink
Shared Channel (PDSCH); identifying a Physical Uplink Control
Channel (PUCCH) resource based on the downlink resource to which
the downlink control signal has been assigned, the PUCCH resource
being a resource to which an ACK/NACK signal for the PDSCH is
assigned; and separating the ACK/NACK signal included in the
identified PUCCH resource from a received signal from a terminal to
which the downlink control signal has been transmitted, wherein the
downlink resource is composed of a plurality of PRB pairs, and any
of a first PRB set and a second PRB set is assigned to each of the
plurality of PRB pairs, and in a case where the downlink control
signal is mapped over the first PRB set and the second PRB set, the
PUCCH resource is identified using an offset value configured for
any of the first PRB set and the second PRB set.
10. A communication method comprising: receiving a downlink control
signal including resource allocation information on Physical
Downlink Shared Channel (PDSCH); identifying a Physical Uplink
Control Channel (PUCCH) resource based on a downlink resource to
which the downlink control signal has been assigned, the PUCCH
resource being a resource to which an ACK/NACK signal for the PDSCH
is assigned; and assigning the ACK/NACK signal to the identified
PUCCH resource, wherein the downlink resource is composed of a
plurality of PRB pairs, and any of a first PRB set and a second PRB
set is assigned to each of the plurality of PRB pairs, and in a
case where the downlink control signal is mapped over the first PRB
set and the second PRB set, the PUCCH resource is identified using
an offset value configured for any of the first PRB set and the
second PRB set.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a base station, a
terminal, and a communication method.
BACKGROUND ART
[0002] In recent years, Machine-Type Communications (MTC), which
uses a cellular network, has been under study (see, e.g.,
Non-Patent Literature (hereinafter, referred to as "NPL") 1). The
applications of MTC possibly include automatic meter reading of
smart meters, and/or the inventory control, logistics management
and/or pet and domestic animal control using position information,
and mobile payment and/or the like. In MTC, it is expected that a
terminal that supports MTC (may be referred to as an MTC terminal
or MTC UE) is connected to a network. Although a large number of
MTC terminals are arranged, it is predicted that the amount of
traffic of each one of the MTC terminals is not so large.
Therefore, the MTC terminals are desired to be low costs and low
power consumption. Moreover, the MTC terminal is possibly placed in
the underground or the like of a building to which an electric wave
is unlikely to reach, so that coverage enhancement is also in
demand.
[0003] In extension of LTE-Advanced, which has been standardized by
3GPP, limiting the resource used by an MTC terminal for
communication to be not greater than 6 physical resource blocks
(PRBs) regardless of a system band has been under study for the
purpose of achieving low-costs for MTC terminals. When the system
band is wider than 6 PRBs, the MTC terminal receives only part of
the system band and performs transmission and reception. The PRB
used for transmission and reception is changeable by retuning. This
resource not greater than 6 PRBs is called "Narrowband." It is
defined that this Narrowband is composed of contiguous PRBs.
[0004] Moreover, studies have been conducted on using MPDCCH (PDCCH
for MTC) obtained by extending Enhanced Physical Downlink Control
CHannel (EPDCCH), as a control signal for MTC terminals. MPDCCH is
mapped in a PDSCH region in Narrowband. Moreover, in MTC, a method
in which MPDCCH is assigned to all 6 PRB pairs included in
Narrowband has been under study for coverage enhancement. In
EPDCCH, there are 16 Enhanced Resource Element Groups (EREGs) per
PRB pair, and when the number of EREGs per Enhanced CCE (ECCE) is
set to 4, the number of ECCEs of 6 PRB pairs becomes 24 ECCEs. In
addition, ECCE is a unit for assigning EPDCCH, and EREG is a unit
used for mapping ECCE to a Resource Element (RE). Moreover, a PRB
pair is a resource unit and is composed of 1 subframe (time
domain).times.12 subcarriers (frequency), and when a resource on
only the frequency domain is to be indicated, the resource may only
be referred to as "PRB."
[0005] For MPDCCH to be configured for MTC terminals, mapping of
MPDCCH composed of 4 PRB pairs (4 PRB set) or MPDCCH composed of 2
PRB pairs (2 PRB set) in 6 PRB pairs has been under study.
Moreover, 1, 2, 4, 8, 16, and 24 have been discussed as the
aggregation levels of MPDCCH. No that, each of the aggregation
levels indicates the number of ECCEs forming MPDCCH. For
aggregation levels=1, 2, 4, and 8, MPDCCH is mapped in 4 PRB set or
2 PRB set in a closed manner, and for aggregation level=16, one
MPDCCH is mapped to all 16 ECCEs in 4 PRB set.
[0006] Furthermore, for an MTC terminal with low channel quality,
mapping of one MPDCCH to all 6 PRB pairs in Narrowband, which
overlap with an MPDCCH resource composed of 4 PRB pairs and 2 PRB
pairs has been under study. In this case, aggregation level=24,
which may be simply referred to also as "24 ECCEs."
CITATION LIST
Non-Patent Literature
[0007] NPL 1 [0008] 3GPP TR 36.888 V12.0.0, and "Machine-Type
Communications (MTC) User Equipments (UEs) based on LTE (Release
12)," June 2013.
SUMMARY OF INVENTION
Technical Problem
[0009] As with the traditional terminals, an MTC terminal receives
MPDCCH, which is a downlink (DL) control signal, receives the
downlink data (PDSCH) indicated by MPDCCH, and transmits an
ACK/NACK signal of the received result via PUCCH, which is an
uplink (UL) control signal. In order for each MTC terminal to
identify a PUCCH resource for an MTC terminal in this case, use of
an offset (called "N_pucch") configured for each PRB set, as in the
case of EPDCCH, has been discussed.
[0010] However, no studies have been conducted on how to define the
offset (N_pucch) for "24 ECCEs" for mapping one MPDCCH to all 6 PRB
pairs in Narrowband.
[0011] Thus, an aspect of the present disclosure provides a base
station, a terminal, and a communication method each making it
possible to efficiently identify a PUCCH resource of a case where
one MPDCCH is mapped to all 6 PRB pairs in Narrowband.
Solution to Problem
[0012] A base station according to an aspect of the present
disclosure includes: a signal assignment section that assigns a
downlink control signal to a downlink resource, the downlink
control signal including resource allocation information on
Physical Downlink Shared Channel (PDSCH); an identifying section
that identifies a Physical Uplink Control Channel (PUCCH) resource
based on the downlink resource to which the downlink control signal
has been assigned, the PUCCH resource being a resource to which an
ACK/NACK signal for the PDSCH is assigned; and a signal separating
section that separates the ACK/NACK signal included in the
identified PUCCH resource from a received signal from a terminal to
which the downlink control signal has been transmitted, in which
the downlink resource is composed of a plurality of PRB pairs, and
any of a first PRB set and a second PRB set is assigned to each of
the plurality of PRB pairs, and in a case where the downlink
control signal is mapped over the first PRB set and the second PRB
set, the identifying section identifies the PUCCH resource, using
an offset value configured for any of the first PRB set and the
second PRB set.
[0013] A terminal according to an aspect of the present disclosure
includes: a receiving section that receives a downlink control
signal including resource allocation information on Physical
Downlink Shared Channel (PDSCH); and an identifying section that
identifies a Physical Uplink Control Channel (PUCCH) resource based
on a downlink resource to which the downlink control signal has
been assigned, the PUCCH resource being a resource to which an
ACK/NACK signal for the PDSCH is assigned; and a signal assignment
section that assigns the ACK/NACK signal to the identified PUCCH
resource, in which the downlink resource is composed of a plurality
of PRB pairs, and any of a first PRB set and a second PRB set is
assigned to each of the plurality of PRB pairs, and in a case where
the downlink control signal is mapped over the first PRB set and
the second PRB set, the identifying section identifies the PUCCH
resource, using an offset value configured for any of the first PRB
set and the second PRB set.
[0014] It should be noted that general or specific embodiments may
be implemented as a system, an apparatus, a method, an integrated
circuit, a computer program or a storage medium, or any selective
combination of the system, the apparatus, the method, the
integrated circuit, the computer program, and the storage
medium.
[0015] According to an aspect of the present disclosure, it is made
possible to efficiently identify a PUCCH resource of a case where
one MPDCCH is mapped to all 6 PRB pairs in Narrowband.
[0016] Additional benefits and advantages of the disclosed
embodiments will become apparent from the specification and
drawings. The benefits and/or advantages may be individually
obtained by the various embodiments and features of the
specification and drawings, which need not all be provided in order
to obtain one or more of such benefits and/or advantages.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a conceptual diagram of a PUCCH resource;
[0018] FIG. 2A is a diagram illustrating an example of an MPDCCH
mapping method (Option 1);
[0019] FIG. 2B is another diagram illustrating another example of
the MPDCCH mapping method (Option 1);
[0020] FIG. 3A is a diagram illustrating an example of an MPDCCH
mapping method (Option 2);
[0021] FIG. 3B is another diagram illustrating the example of the
MPDCCH mapping method (Option 2)
[0022] FIG. 4 is a block diagram illustrating a main configuration
of a base station:
[0023] FIG. 5 is a block diagram illustrating a main configuration
of a terminal:
[0024] FIG. 6 is a block diagram illustrating a configuration of
the base station;
[0025] FIG. 7 is a block diagram illustrating a configuration of
the terminal;
[0026] FIG. 8 is a diagram illustrating an example of a PUCCH
resource identification method according to Operation Example 1 of
Embodiment 1;
[0027] FIG. 9 is a conceptual diagram of a PUCCH resource;
[0028] FIG. 10 is a diagram provided for describing a problem of
Embodiment 3:
[0029] FIG. 11 is another diagram provided for describing the
problem of Embodiment 3:
[0030] FIG. 12A is a diagram illustrating an example of an MPDCCH
mapping method according to Operation Example 6 of Embodiment
3;
[0031] FIG. 12B is a diagram illustrating an example of an MPDCCH
mapping method according to Operation Example 6 of Embodiment
3;
[0032] FIG. 12C is a diagram illustrating an example of an MPDCCH
mapping method according to Operation Example 6 of Embodiment
3:
[0033] FIG. 13A is a diagram illustrating a 4 PRB set assignment
example according to a variation; and
[0034] FIG. 13B is a diagram illustrating a 2 PRB set assignment
example according to a variation.
DESCRIPTION OF EMBODIMENTS
[0035] (Knowledge as Foundation of Present Disclosure)
[0036] Use of an offset (N_pucch) for identifying a PUCCH resource
directed to an MTC terminal makes it possible to distinguish
between a traditional terminal PUCCH resource and an MTC terminal
PUCCH resource and thus to avoid a collision of PUCCH resources.
Moreover, N_pucch can avoid a collision of PUCCH resources between
MTC terminals of different repetition levels when an indication is
given for each repetition level. Thus, a distance problem that
occurs when signals of terminals having mutually different
distances to a base station are multiplexed can be solved.
[0037] In N_pucch for a single MTC, a collision of PUCCH resources
between a plurality of MTC terminals of the same repetition level
cannot be avoided, however.
[0038] In this respect, for PUCCH resources of MTC terminals of the
same repetition level, it may be possible to identify a resource of
PUCCH format 1a/1b for transmitting an ACK/NACK based on mapping of
a DL control signal (MPDCCH) by which DL assignment indicating
transmission of a DL data signal as in the case of EPDCCH.
[0039] In EPDCCH, offset N.sub.PUCCH,q.sup.(e1) (hereinafter,
referred to as "N_pucch, q" for simplicity) is configured for each
EPDCCH-PRB-set q=0, 1, and a PUCCH resource is identified from an
ECCE number. In EPDCCH, a resource (resource number) of PUCCH
format 1a/1b is identified by the following expressions.
distributed assignment : n PUCCH ( 1 , p ~ 0 ) = n ECCE , q +
.DELTA. ARO + N PUCCH , q ( e 1 ) localized assignment : n PUCCH (
1 , p ~ 0 ) = n ECCE , q N RB ECCE , q N RB ECCE , q + n ' +
.DELTA. ARO + N PUCCH , q ( e 1 ) [ Expression 1 ] ##EQU00001##
[0040] In Expression 1, n.sub.ECCE, q represents an offset by the
original ECCE number to which a DCI (Downlink Control Information)
is mapped in the q-th EPDCCH PRB set. Moreover, .DELTA..sub.ARO
represents an offset indicated by 2-bit ARO (ACK/NACK Resource
Offset) included in the DCI, and the offset takes values of -2, -1,
0, and +2 in case of FDD. Moreover. N.sub.PUCCH, q(e1) is indicated
for each terminal by a higher layer. Moreover, Na.sup.ECCE,q
represents the number of ECCEs per RB, and n' represents an offset
based on an antenna port.
[0041] FIG. 1 is a conceptual diagram of the PUCCH resource
mentioned above.
[0042] As illustrated in FIG. 1, by configuring offset values
N.sub.PUCCH,0.sup.(e1) and N.sub.PUCCH,1.sup.(e1) to have values
distant from each other, the PUCCH resources corresponding to the
respective PRB sets are mapped so as not to overlap with each
other, so that a collision of PUCCH resources can be avoided.
Moreover, by configuring N.sub.PUCCH,0.sup.(e1) and N.sub.PUCCH,
1.sup.(e1) to have values close to each other, the PUCCH resources
corresponding to the respective PRB sets are mapped so as to
overlap with each other, so that the entirety of PUCCH resources
can also be reduced.
[0043] It is conceivable to identify a PUCCH resource for MPDCCH as
in the case of EPDCCH. In this case, for the MPDCCH to be mapped in
a PRB set composed of 4 PRB pairs or 2 PRB pairs, a PUCCH resource
can be identified by a method similar to the method for EPDCCH
mentioned above.
[0044] There is, however, a problem in that the same method as that
for EPDCCH cannot be applied for a PUCCH resource of a case where
MPDCCH is mapped to 24 ECCEs in Narrowband (i.e., a case where
MPDCCH is mapped over 4 PRB set and 2 PRB set), and it is thus
impossible to identify a resource. Note that, although it is
conceivable to separately indicate an offset corresponding to
MPDCCH of 24 ECCEs, the amount of signaling increases in this
case.
[0045] Hereinafter, a description will be given of a method for
identifying a PUCCH resource without any increase in the amount of
signaling in a case where MPDCCH is mapped to 24 ECCEs in a
narrowband.
[0046] Hereinafter, a detailed description will be given of an
embodiment of the present disclosure with reference to the
accompanying drawings.
[0047] [Description of MTC 24 ECCEs]
[0048] As mentioned above, MPDCCH of 24 ECCEs used in MTC is mapped
to all REs which are included in 6 PRB pairs in Narrowband and
which are available for MPDCCH. Hereinafter, a description will be
given of two Options 1 and 2 each conceivable as a mapping method
for MPDCCH of 24 ECCEs.
[0049] (Option 1: FIGS. 2A and 2B)
[0050] In Option 1, MPDCCH of 24 ECCEs is mapped to a frequency
first (Frequency first). More specifically, in Narrowband, a symbol
sequence of MPDCCH is mapped from an OFDM symbol with a low OFDM
symbol number in ascending order of frequency while vertically
crossing over PRB pairs, and then moves to the next OFDM symbol and
is mapped in ascending order of frequency while vertically crossing
over PRB pairs, likewise.
[0051] FIGS. 2A and 2B illustrate an MPDCCH mapping example of
Option 1.
[0052] In FIG. 2A, 2 PRB set is assigned to PRB pairs #0 and #1,
and 4 PRB set is assigned to PRB pairs #2 to #5. In FIG. 2A, MPDCCH
of 24 ECCEs is mapped to all REs available for MPDCCH without
distinction between 2 PRB set resources (PRB pairs #0, #1) and 4
PRB set resources (PRB pairs #2 to #5).
[0053] In FIG. 2B, 2 PRB set is assigned to PRB pairs #2 and #3,
and 4 PRB set is assigned to PRB pairs #0, #1, #4, and #5. In FIG.
2B, as in FIG. 2A, MPDCCH of 24 ECCEs is mapped to all REs
available for MPDCCH without distinction between 2 PRB set
resources (PRB pairs #2, #3) and 4 PRB set resources (PRB pairs #0,
#1, #4, #5).
[0054] (Option 2: FIGS. 3A and 3B)
[0055] In Option 2, MPDCCH of 24 ECCEs is mapped to an MPDCCH PRB
set first in Narrowband. Accordingly, the mapping order of MPDCCH
is changed depending on which PRB pair the PRB set is assigned
to.
[0056] FIGS. 3A and 3B illustrate an MPDCCH mapping example of
Option 2 in which MPDCCH is mapped to 4 PRB set, first. More
specifically, MPDCCH is first mapped to REs in the 4 PRB set and
then mapped to REs in 2 PRB set. Note that, mapping in 4 PRB set
and 2 PRB set is performed Frequency first as in EPDCCH. More
specifically, in PRB pairs in a PRB set, the symbol sequence of
MPDCCH is mapped from an OFDM symbol with a low OFDM symbol number
in ascending order of frequency while vertically crossing over PRB
pairs, and then moves to the next OFDM symbol and is mapped in
ascending order of frequency while vertically crossing over PRB
pairs, likewise.
[0057] In FIG. 3A, 2 PRB set is assigned to PRB pairs #0 and #1,
and 4 PRB set is assigned to PRB pairs #2 to #5. Accordingly, in
FIG. 3A. MPDCCH of 24 ECCEs is mapped to PRB pairs #2 to #5 to
which 4 PRB set is assigned, and then mapped to PRB pairs #0 and #1
to which 2 PRB set is assigned.
[0058] In FIG. 3B, 2 PRB set is assigned to PRB pairs #2 and #3,
and 4 PRB set is assigned to PRB pairs #0, #1, #4, and #5.
Accordingly, in FIG. 3B, MPDCCH of 24 ECCEs is mapped to PRB pairs
#0, #1, #4, and #5 to which 4 PRB set is assigned, and then mapped
to PRB pairs #2 and #3 to which 2 PRB set is assigned.
[0059] Note that, hereinafter, in any of Options, the minimum ECCE
number of a case where MPDCCH of 24 ECCE is detected is assumed to
be n.sub.ECCE,q=0.
[0060] [Overview of Communication System]
[0061] A communication system according to each embodiment of the
present disclosure includes base station 100 and terminal 200 each
supporting the LTE-Advanced system, for example. Terminal 200 is an
MTC terminal, for example.
[0062] FIG. 4 is a block diagram illustrating a main configuration
of base station 100 according to the embodiment of the present
disclosure. In base station 100 illustrated in FIG. 4, signal
assignment section 105 assigns a downlink control signal (MPDCCH)
including PDSCH resource assignment information to a downlink
resource (Narrowband). PUCCH resource identifying section 108
identifies the PUCCH resource to which an ACK/NACK for PDSCH is to
be assigned, based on the downlink resource to which the downlink
control signal has been assigned. Signal separating section 109
separates the ACK/NACK signal included in the identified PUCCH
resource from a received signal from the terminal to which the
downlink control signal has been transmitted.
[0063] Moreover. FIG. 5 is a block diagram illustrating a main
configuration of terminal 200 according to each embodiment of the
present disclosure. In terminal 200 illustrated in FIG. 5, MPDCCH
receiving section 207 receives a downlink control signal (MPDCCH)
including PDSCH resource assignment information. PUCCH resource
identifying section 208 identifies the PUCCH resource to which an
ACK/NACK signal for PDSCH is to be assigned, based on the downlink
resource to which the downlink control signal has been assigned.
Signal assignment section 211 assigns an ACK/NACK signal to the
identified PUCCH resource.
[0064] In addition, the above-mentioned downlink resource
(Narrowband) is composed of a plurality of PRB pairs, and any of
the 1st PRB set and the 2nd PRB set is assigned to each of the
plurality of PRB pairs. PUCCH resource identifying section 108
(208) identifies the PUCCH resource using the offset value
configured for any of the 1st PRB set and the 2nd PRB set in a case
where a down control signal is mapped over the 1st PRB set and the
2nd PRB set described above.
Embodiment 1
[Configuration of Base Station]
[0065] FIG. 6 is a block diagram illustrating a configuration of
base station 100 according to the present embodiment. In FIG. 6,
base station 100 includes aggregation level configuration section
101, MPDCCH generation section 102, error correction coding section
103, modulation section 104, signal assignment section 105,
transmitting section 106, receiving section 107, PUCCH resource
identifying section 108, signal separating section 109, PUCCH
receiving section 110, demodulation section 111, and error
correction decoding section 112.
[0066] Aggregation level configuration section 101 configures an
aggregation level for an MTC terminal based on receiving quality of
the MTC terminal and the number of information bits of MPDCCH (not
illustrated) which are held by base station 100. Aggregation level
configuration section 101 outputs the configured aggregation level
to MPDCCH generation section 102.
[0067] MPDCCH generation section 102 generates MPDCCH which is the
control information directed to the MTC terminal. More
specifically, MPDCCH generation section 102 generates the
information bit of MPDCCH, applies error correction coding thereto,
generates a transmission bit sequence by rate matching from the
aggregation level inputted from aggregation level configuration
section 101, and the number of REs available for MPDCCH, and
outputs the transmission bit sequence to signal assignment section
105. MPDCCH includes DL assignment information indicating PDSCH
resource allocation, and UL assignment information indicating PUSCH
resource allocation, for example. Moreover, the DL assignment
information is outputted to signal assignment section 105, and the
UL assignment information is outputted to signal separating section
109.
[0068] Error correction coding section 103 applies error correction
coding to a transmission data signal (DL data signal) or higher
layer signaling and outputs the encoded signal to modulation
section 104.
[0069] Modulation section 104 applies modulation processing to the
signal received from error correction coding section 103 and
outputs the modulated data signal to signal assignment section
105.
[0070] Signal assignment section 105 assigns the signal (including
data signal) received from modulation section 104, and the control
signal (MPDCCH) received from MPDCCH generation section 102 to a
predetermined downlink resource. For example, when the aggregation
level of MPDCCH is 1, 2, 4, or 8, signal assignment section 105
assigns MPDCCH to either PRB set 0 or PRB set 1 in Narrowband, and
when the aggregation level of MPDCCH is 16, signal assignment
section 105 assigns MPDCCH to a PRB set having the number of PRBs
equal to 4. Furthermore, when the aggregation level is 24 (24
ECCEs), signal assignment section 105 assigns MPDCCH to all ECCEs
in Narrowband over PRB set 0 and PRB set 1 in Narrowband. Moreover,
signal assignment section 105 assigns a signal directed to an MTC
terminal to Narrowband among a transmission data signal and higher
layer signaling. In this manner, a transmission signal is formed by
assigning a control signal (MPDCCH) and a data signal (PDSCH) to a
predetermined resource. The transmission signal thus formed is
outputted to transmitting section 106. Moreover, signal assignment
section 105 outputs assignment information (e.g., the PRB set
number, the minimum ECCE number, and ARO included in the DL
assignment information to which MPDCCH has been mapped) indicating
the resource to which MPDCCH is assigned, to PUCCH resource
identifying section 108.
[0071] Transmitting section 106 applies radio transmission
processing, such as up-conversion, to the transmission signal
inputted from signal assignment section 105, and transmits the
processed signal to terminal 200 via an antenna.
[0072] Receiving section 107 receives, via an antenna, the signal
transmitted from terminal 200, and applies radio reception
processing, such as down-conversion, to the received signal, and
outputs the processed signal to signal separating section 109.
[0073] PUCCH resource identifying section 108 identifies a PUCCH
resource to which an ACK/NACK signal for the data signal (PDSCH)
indicated by the MPDCCH is assigned, based on the downlink resource
which is indicated by the assignment information inputted from
signal assignment section 105 and to which the MPDCCH is assigned.
PUCCH resource identifying section 108 outputs the information
indicating the identified PUCCH resource to signal separating
section 109. In addition, the PUCCH resource identifying method in
PUCCH resource identifying section 108 will be described in detail,
hereinafter.
[0074] Signal separating section 109 separates a UL data signal
from the received signal based on the information inputted from
MPDCCH generation section 102 and outputs the separated signal to
demodulation section 111. Moreover, signal separating section 109
separates the signal (including ACK/NACK signal) included in the
PUCCH resource from the received signal based on the information
inputted from PUCCH resource identifying section 108 and outputs
the signal to PUCCH receiving section 110.
[0075] PUCCH receiving section 110 determines an ACK and NACK from
the signal (PUCCH) inputted from signal separating section 109 and
indicates the determination result to a higher layer.
[0076] Demodulation section 111 applies demodulation processing to
the signal inputted from signal separating section 109 and outputs
the signal acquired by the demodulation processing to error
correction decoding section 112.
[0077] Error correction decoding section 112 decodes the signal
inputted from demodulation section 111 and acquires a received data
signal from terminal 200.
[0078] [Configuration of Terminal]
[0079] FIG. 7 is a block diagram illustrating a configuration of
terminal 200 according to the present embodiment. In FIG. 7,
terminal 200 includes receiving section 201, signal separating
section 202, demodulation section 203, error correction decoding
section 204, error determination section 205, ACK/NACK generation
section 206, MPDCCH receiving section 207, PUCCH resource
identifying section 208, error correction coding section 209,
modulation section 210, signal assignment section 211, and
transmitting section 212.
[0080] Receiving section 201 identifies to which Narrowband within
a system band the signal has been assigned, based on a
predetermined pattern, or information (not illustrated) indicated
by a higher layer, and applies retuning to the identified
Narrowband. Receiving section 201 then receives a received signal
via an antenna, applies reception processing, such as
down-conversion, to the received signal, and then outputs the
processed signal to signal separating section 202.
[0081] Signal separating section 202 outputs, to MPDCCH receiving
section 207, the signal (MPDCCH signal) mapped to a PRB to which
MPDCCH may have been assigned. Moreover, signal separating section
202 separates a DL data signal and higher layer signaling from the
received signal based on the DL assignment information inputted
from MPDCCH receiving section 207, and outputs the DL data signal
and higher layer signaling to demodulation section 203.
[0082] Demodulation section 203 demodulates the signal received
from signal separating section 202 and outputs the demodulated
signal to error correction decoding section 204.
[0083] Error correction decoding section 204 decodes the
demodulated signal received from demodulation section 203 and
outputs the received data signal acquired by decoding. Moreover,
the received data signal is outputted to error determination
section 205.
[0084] Error determination section 205 detects an error by CRC of
the received data signal and outputs the detection result to
ACK/NACK generation section 206.
[0085] ACK/NACK generation section 206 generates an ACK when there
is no error, and generates a NACK when there is an error, based on
the detection result of the received data signal inputted from
error determination section 205, and outputs the generated ACK/NACK
signal to a higher layer and signal assignment section 211.
[0086] MPDCCH receiving section 207 detects MPDCCH which is a
control signal including DL assignment information or UL assignment
information by attempting reception of the MPDCCH signal received
from signal separating section 202 with respect to search space for
each PRB set 0 and PRB set 1, and "24 ECCEs" assigned to all ECCEs
in Narrowband over PRB set 0 and PRB set 1. MPDCCH receiving
section 207 outputs the DL assignment information detected as a
signal directed to terminal 200 of MPDCCH receiving section 207, to
signal separating section 202, and outputs the UL assignment
information to signal assignment section 211. Moreover, MPDCCH
receiving section 207 outputs the assignment information indicating
the PRB set number, the minimum ECCE number, and ARO included in DL
the assignment information, to which the MPDCCH has been mapped, to
PUCCH resource identifying section 208.
[0087] PUCCH resource identifying section 208 identifies the PUCCH
resource to which an ACK/NACK for the received data signal is
assigned, based on the assignment information inputted from MPDCCH
receiving section 207 (PRB set number, the minimum ECCE number, and
ARO), and the N_pucch information that is previously indicated by a
higher layer. PUCCH resource identifying section 208 outputs the
information indicating the identified PUCCH resource to signal
assignment section 211. No that, the PUCCH resource identifying
method in PUCCH resource identifying section 208 will be described
in detail, hereinafter.
[0088] Error correction coding section 209 applies error correction
coding to the transmission data signal (UL data signal) and outputs
the encoded data signal to modulation section 210.
[0089] Modulation section 210 modulates the data signal received
from error correction coding section 209 and outputs the modulated
data signal to signal assignment section 211.
[0090] Signal assignment section 211 assigns the data signal
inputted from modulation section 210 to a resource based on the UL
assignment information received from MPDCCH receiving section 207
and outputs the resultant to transmitting section 212. Moreover,
signal assignment section 211 assigns the ACK/NACK signal inputted
from ACK/NACK generating section 206 to a PUCCH resource based on
the PUCCH resource allocation information inputted from PUCCH
resource identifying section 208, and outputs the resultant to
transmitting section 212.
[0091] Transmitting section 212 identifies the resource
corresponding to Narrowband to which UL data is assigned, based on
the predetermined pattern and applies retuning. Transmitting
section 212 applies transmission processing, such as up-conversion,
to the signal inputted from signal assignment section 211, and
transmits the processed signal via an antenna.
[0092] [Operations of Base station 100 and Terminal 200]
[0093] The operations of base station 100 and terminal 200 each
configured in the manner described above will be described in
detail.
[0094] In the present embodiment, in a case where MPDCCH is mapped
over a plurality of PRB sets (4 PRB set and 2 PRB set) (i.e., case
of MPDCCH of 24 CCEs), base station 100 (PUCCH resource identifying
section 108) and terminal 200 (PUCCH resource identifying section
208) identify a PUCCH resource, using an offset value (N_pucch)
configured for any of the plurality of PRB sets.
[0095] Hereinafter, Operation Examples 1 and 2 according to the
present embodiment will be described.
[0096] (Operation Example 1)
[0097] In Operation Example 1, when detecting MPDCCH of 24 ECCEs,
terminal 200 (MTC terminal) identifies a PUCCH resource, using an
offset value (MTC N_pucch) configured for a PRB set assigned to a
PRB pair having a minimum PRB number among the PRB sets in
Narrowband in both Options 1 and 2.
[0098] For example, in FIG. 2A of Option 1, and FIG. 3A of Option
2, terminal 200 identifies a PUCCH resource, using N_pucch
corresponding to the 2 PRB set assigned to PRB pair #0. Meanwhile,
in FIG. 2B of Option 1, and FIG. 3B of Option 2, terminal 200
identifies a PUCCH resource, using N_pucch corresponding to 4 PRB
set assigned to PRB #0.
[0099] Moreover, base station 100 identifies, as in the case of
terminal 200, a PUCCH resource to which an ACK/NACK signal is
assigned, using an offset value (MTC N_pucch) configured for a PRB
set assigned to a PRB pair having a minimum PRB number among the
PRB sets in Narrowband to which MPDCCH is assigned.
[0100] In a case where the PUCCH resource corresponding to MPDCCH
of 24 ECCEs is identified in the manner described above, the offset
value N_pucch to be configured for MPDCCH of 24 ECCEs differs in
accordance with assignment of a PRB set of MPDCCH to a PRB pair, as
described above. Accordingly, the PUCCH resource corresponding to
MPDCCH of 24 ECCEs can be switched by assignment of a PRB set of
MPDCCH.
[0101] FIG. 8 illustrates a PUCCH resource allocation example of a
case where two Narrowbands 1 and 3 are used for different MTC
terminals (terminals 200), and MPDCCH of 24 ECCEs is detected in
both Narrowbands.
[0102] In FIG. 8, N_pucch, 0 is configured for 2 PRB set, and
N_pucch, 1 is configured for 4PRB set. Moreover, assignment of PRB
set differs between two Narrowbands illustrated in FIG. 8. More
specifically, in Narrowband 1, as in FIG. 2A, 2 PRB set is assigned
to PRB pairs #0 and #1, and 4 PRB set is assigned to PRB pairs #2
to #5. Meanwhile, in Narrowband 3, as in FIG. 2B, 2 PRB set is
assigned to PRB pairs #14 and #15, and 4PRB set is assigned to PRB
pairs #12, #13, #16, and #17.
[0103] In this case, the MTC terminal that uses Narrowband 1
identifies a PUCCH resource, using N_pucch, 0 configured for 2 PRB
set assigned to PRB pair #0 having the minimum PRB number.
Meanwhile, the MTC terminal that uses Narrowband 3 identifies a
PUCCH resource, using N_pucch, 1 configured for 4 PRB set assigned
to PRB pair #12 having the minimum PRB number.
[0104] Accordingly, as illustrated in FIG. 8, even when MPDCCH of
24 ECCEs has been simultaneously mapped in two Narrowbands 1 and 3,
each of the MTC terminals identifies a PUCCH resource, using
different N_pucch, so that a collision of PUCCH resources can be
prevented.
Operation Example 2
[0105] In Operation Example 2, when detecting MPDCCH of 24 ECCEs in
both Options 1 and 2, terminal 200 (MTC terminal) identifies a
PUCCH resource, using an offset value (N_pucch, 0) configured for a
PRB set having the minimum PRB set number among the PRB sets in
Narrowband.
[0106] N_pucch, 0 is N_pucch configured for PRB set 0 (first PRB
set), herein. Which PRB set is PRB set 0 or PRB set 1 among 2 PRB
set and 4 PRB set may be indicated during configuration performed
in a higher layer (RRC signaling), or one of the PRB sets may be
previously defined to be PRB set 0. Moreover, N_pucch, 0 and
N_pucch, 1 are indicated to terminal 200 by the higher layer (RRC
signaling). The higher layer signaling may be an SIB for MTC which
can be received in common by MTC terminals or signaling specific to
terminal 200.
[0107] Moreover, as in the case of terminal 200, base station 100
identifies a PUCCH resource to which an ACK/NACK signal is
assigned, using an offset value (N_pucch, 0) configured for a PRB
set having the minimum PRB set number among PRB sets in Narrowband
to which MPDCCH is assigned.
[0108] Thus, when the PUCCH resource corresponding to MPDCCH of 24
ECCEs is to be identified in the manner described above, N_pucch, 0
is always used independently of which PRB pair each PRB set is
assigned to in Narrowband.
[0109] Moreover, when 24 ECCEs are used without assumption of
MU-MIMO, another MPDCCH is not mapped in Narrowband in which 24
ECCEs are mapped. Therefore, in order to avoid generating an
unnecessary blank resource, it is desirable to use a PUCCH resource
having a low resource number. In this respect, using N_pucch, 0 in
a case where a PUCCH resource corresponding to MPDCCH of 24 ECCEs
is to be identified, it can be expected that a PUCCH resource
having a low resource number is configured. Thus, reduction of
PUCCH resources can be achieved, and a PUSCH resource can be
secured more widely. Note that, it is assumed herein that the value
of N_pucch, 0 is smaller than the value of N_pucch, 1.
[0110] Moreover, when MPDCCH is transmitted in another Narrowband
and the same N_pucch, 0 and n.sub.ECCE, 0=0 are used under
assumption of MU-MIMO, a collision of PUCCH resources occurs.
However, the collision of PUCCH resources can be avoided by ARO in
this case.
Variation of Operation Example 2
[0111] Note that, in Operation Example 2, it is possible to set a
rule that, when an MTC terminal detects MPDCCH of 24 ECCEs, a PUCCH
resource is identified using N_pucch, 1. In this case, configuring
N_pucch, 1 to have a value smaller than N_pucch, 0 makes it
possible to achieve reduction of PUCCH resources.
[0112] Moreover, it is possible to set a rule that, when an MTC
terminal detects MPDCCH of 24 ECCEs, a PUCCH resource is identified
using one of N_pucch, 0 and N_pucch, 1 whichever has a smaller
value than the other. In this case, reduction of PUCCH resources
can be achieved irrespective of the magnitude relationship of
N_pucch, 0 and N_pucch, 1.
[0113] Moreover, it is possible to set a rule that, when an MTC
terminal detects MPDCCH of 24 ECCEs, a PUCCH resource is identified
using N_pucch corresponding to 4 PRB set or N_pucch corresponding
to 2 PRB set. In this case, configuring N_pucch corresponding to 4
PRB set or N_pucch corresponding to 2 PRB set to have a small value
makes it possible to achieve reduction of PUCCH resources.
[0114] Operation Examples 1 and 2 according to the present
embodiment have been described thus far.
[0115] As described above, in the present embodiment, in a case
where MPDCCH is mapped over a plurality of PRB sets, base station
100 and terminal 200 identify a PUCCH resource, using N_pucch, q
corresponding to any of the plurality of PRB sets q to which the
MPDCCH is mapped.
[0116] In the manner described above, base station 100 and terminal
200 can identify the PUCCH resource corresponding to MPDCCH mapped
over a plurality of PRB sets, as with 24 ECCEs, without addition of
new signaling. That is, according to the present embodiment, the
PUCCH resource of the case where one MPDCCH is mapped to all 6 PRB
pairs in Narrowband can be efficiently identified.
[0117] In addition, in MPDCCH mapping of Option 2, in the operation
example described above, a description has been given with an
example of a case where an assumption is made that, PRB set 0
(first PRB set) indicated by a higher layer is 4 PRB set while PRB
set 1 (second PRB set) is 2 PRB set, and MPDCCH is mapped to 4 PRB
set first. It is, however, MPDCCH may be mapped to PRB set 1
(second PRB set) first.
Embodiment 2
[0118] A base station and a terminal according to Embodiment 2 have
basic configurations common to base station 100 and terminal 200
according to Embodiment 1, so that a description will be given
while FIGS. 6 and 7 are incorporated herein.
[0119] In Embodiment 1, a description has been given of the case
where an assumption is made that different offset values N_pucch
are configured for a plurality of PRB sets. Meanwhile, in this
embodiment, a description will be given of a case where an
assumption is made that a common offset value N_pucch is configured
for a plurality of PRB sets.
[0120] The PUCCH resource corresponding to MPDCCH in this
embodiment will be described, hereinafter.
[0121] For PUCCH of MTC terminals of the same repetition level,
common N.sub.PUCCH.sup.(e1) (hereinafter, simply referred to as
"N_pucch") is configured for PRB sets, and a PUCCH resource is
identified from an ECCE number for each PRB set. The PUCCH resource
(resource number) for transmitting PUCCH format 1a/1b is identified
by the following expressions.
distributed assignment : n PUCCH ( 1 , p ~ 0 ) = n ECCE , q +
.DELTA. ARO + N PUCCH ( e 1 ) + K q localized assignment : n PUCCH
( 1 , p ~ 0 ) = n ECCE , q N RB ECCE , q N RB ECCE , q + n ' +
.DELTA. ARO + N PUCCH ( e 1 ) + K q [ Expression 2 ]
##EQU00002##
[0122] In the case of PRB set 0 (q=0), K.sub.0=0, and in the case
of PRB set 1 (q=1), K.sub.1 represents the number of ECCEs included
in PRB set 0. For example, when PRB set 0 is 4 PRB set (16 ECCEs),
K.sub.1=16, and when PRB set 1 is 2 PRB set (8 ECCEs),
K.sub.1=8.
[0123] FIG. 9 illustrates a conceptual diagram of a PUCCH resource
of the present embodiment.
[0124] As illustrated in FIG. 9, the PUCCH resource (PUCCH set (0))
corresponding to PRB set 0 is identified using N_pucch and an ECCE
number, and the PUCCH resource (PUCCH set (1)) corresponding to PRB
set 1 is identified using N_pucch+ECCE number+K.sub.1 (provided
that, K.sub.1 is the number of ECCEs in PUCCH set (0)). Thus, the
PUCCH resource corresponding to PRB set 0 and the PUCCH resource
corresponding to PRB set 1 are configured to be contiguous
resources. Therefore, when all MPDCCHs are transmitted using
aggregation level 1, the PUCCH resource for PRB set 1 can be mapped
after the PUCCH resource corresponding to PRB set 0 is secured,
without using ARO.
[0125] In the present embodiment, base station 100 and terminal 200
identify a PUCCH resource corresponding to MPDCCH (MPDCCH of 24
ECCEs) mapped over a plurality of PRB sets, using common
N_pucch.
[0126] Hereinafter, Operation Example 3 according to the present
embodiment will be described.
Operation Example 3
[0127] In Operation Example 3, when detecting MPDCCH of 24 ECCEs,
base station 100 and terminal 200 (MTC terminal) identify a PUCCH
resource, using N_pucch configured in common to a plurality of PRB
sets in Narrowband in both Options 1 and 2. At this time, Kq=0
irrespective of which PRB pairs 4 PRB set and 2 PRB set are
assigned to. Moreover, in a case where an assumption is made that
the minimum ECCE number of a case of using MPDCCH of 24 ECCEs is
n.sub.ECCE,q=0, a PUCCH resource (resource number) is identified by
the following expressions.
distributed assignment: n.sub.PUCCH.sup.(1,{tilde over
(p)}.sup.0.sup.)=.DELTA..sub.ARO+N.sub.PUCCH.sup.(e1)
localized assignment: n.sub.PUCCH.sup.(1,{tilde over
(p)}.sup.0.sup.)=n'+.DELTA..sub.ARO+N.sub.PUCCH.sup.(e1)
[Expression 3]
[0128] As described above, when base station 100 and terminal 200
identify the PUCCH resource corresponding to MPDCCH of 24 ECCEs
based on common N_pucch, a PUCCH resource having a low resource
number can be always configured as the PUCCH resource corresponding
to MPDCCH of 24 ECCEs irrespective of assignment of an MPDCCH PRB
set to a PRB pair.
[0129] Thus, it is made possible to avoid a situation where an
unnecessary blank PUCCH resource is secured and to achieve
reduction of PUCCH resources, and as a result of this, the PUSCH
resource can be secured more widely.
[0130] Moreover, according to the present embodiment, base station
100 and terminal 200 can identify the PUCCH resource corresponding
to MPDCCH mapped over a plurality of PRB sets as with 24 ECCEs
without addition of new signaling as in Embodiment 1. That is,
according to the present embodiment, the PUCCH resource of the case
where one MPDCCH is mapped to all 6 PRB pairs in Narrowband can be
efficiently identified.
[0131] Note that, in a case where MPDCCH is transmitted and the
same N_pucch, 0 and n.sub.ECCE, 0=0 are used in another Narrowband
under assumption of MU-MIMO, as in Operation Example 2 of the
Embodiment 1, a collision of PUCCH resources occurs. In this case,
however, the collision of PUCCH resources can be avoided by
ARO.
[0132] Moreover, although the case where the PUCCH resource
corresponding to a PRB set is changed for each PRB set q using
variable K.sub.q has been described in the present embodiment, the
PUCCH resource may be shared between PRB sets q without using
K.sub.q. In this case, the collision of PUCCH resources between PRB
sets q may be avoided by ARO. In particular, it is predicted that
PUCCH resources are not crowded in a case where MPDCCH with a high
aggregation level is used as in MPDCCH of 24 ECCEs, so that the
collision can be avoided by only ARQ. As described above, by
sharing PUCCH resource between PRB sets q, the amount of PUCCH
resource can be reduced. Moreover, in this case as well, the PUCCH
resource of a case where MPDCCH of 24 ECCEs is detected can be
found by an expression similar to that of Operation Example 3.
[0133] Moreover, although a description has been given with the
case where K.sub.1 is set to be the number of ECCEs included in PRB
set 0 in the present embodiment, the value of K.sub.1 is not
limited to this and may be a value indicating 1/2 of the number of
ECCEs included in PRB set 0, for example. When K.sub.1 is set to a
small value such as 1/2 of the number of ECCEs, the entirety of the
amount of PUCCH resources can be reduced. This is effective, for
example, when the probability of a collision of PUCCH resources is
low.
Embodiment 3
[0134] When MPDCCH of 24 ECCEs is mapped to an MPDCCH PRB set first
in Narrowband as described in Option 2, there may be a case where
an MTC terminal erroneously recognizes reception as having received
a maximum aggregation signal of an MPDCCH PRB set to which MPDCCH
has been mapped first (hereinafter, referred to as "erroneous
recognition 1") and a case where an MTC terminal erroneously
recognizes reception as having received a maximum aggregation level
signal of an MPDCCH PRB set to which MPDCCH has been mapped second
(hereinafter, referred to as "erroneous recognition 2").
[0135] Hereinafter, for simplicity of description, an assumption is
made that 24 ECCEs are mapped to PRB set 0, first. Hereinafter, the
erroneous recognition described above and possible problems
associated therewith will be described using FIGS. 10 and 11.
[0136] Erroneous recognition 1 may occur when the number of
transmittable bits which is calculated from the number of REs
available for MPDCCH in PRB set 0 becomes an integral multiple of
the number of after encoding bits of MPDCCH. Moreover, erroneous
recognition 2 may occur, in addition to the above condition of
erroneous recognition 1, when the number of transmittable bits
which is calculated from the number of REs available for MPDCCH in
PRB set 1 becomes an integral multiple of the number of after
encoding bits of MPDCCH.
[0137] FIG. 10 illustrates a case where the number of after
encoding bits of MPDCCH is equal to the number of transmittable
bits in aggregation level 8 (8 ECCEs). Accordingly, the
transmission bit sequence of 24 ECCEs is generated, by rate
matching, as a bit sequence which is three times the bit sequence
by copying the after encoding bits. As illustrated in FIG. 10, the
generated transmission bit sequence is mapped to 16 ECCEs of 4 PRB
set, which is PRB set 0, and then, is mapped to 8 ECCEs of 2 PRB
set, which is PRB set 1.
[0138] When the number of after encoding bits of MPDCCH is equal to
the number of transmittable bits in another aggregation level, it
is not necessary to reduce the bits at the time of rate matching.
For this reason, the transmission bit sequence of the first-half 16
ECCEs and the second-half 8 ECCEs of the transmission bit sequence
of 24 ECCEs illustrated in FIG. 10 becomes a bit sequence
receivable as 16 ECCEs or 8 ECCEs (i.e., bit sequence is one that
is erroneously recognized as 16 ECCEs or 8 ECCEs) in an MTC
terminal when the reception quality in the MTC terminal is
high.
[0139] Note that, whether bits are reduced or not at the time of
rate matching differs depending on the number of REs available for
MPDCCH transmission. Moreover, the number of REs available for
MPDCCH transmission is variable depending on the PDCCH length, the
number of CRS ports, the number of CSI-RS ports, and/or CP length,
for example. Therefore, it is difficult to cover all patterns as to
under what conditions the problems of erroneous recognition occur
for MPDCCH. Meanwhile, in PDCCH, when a similar problem occurs, the
measure to add a padding bit to information bits is taken. This is
because the number of REs used for transmission of each aggregation
level is fixed. Moreover, in EPDCCH, this problem is avoided by
mapping of EPDCCH to REs is configured to be Frequency first.
[0140] Moreover, the erroneous recognition occurs when the actual
reception quality of an MTC terminal is greater than the reception
quality of the MTC terminal which has been predicted by the base
station, and MPDCCH can be received in the MTC terminal with
aggregation level 16 of 4 PRB set or aggregation level 8 of 2 PRB
set, each of which is an aggregation level lower than 24 ECCEs.
When erroneous recognition of this aggregation level occurs, there
arises a problem in that a PUCCH resource is erroneously
selected.
[0141] More specifically, in a case where an MTC terminal
erroneously recognizes reception as having received MPDCCH of
aggregation level 16 of 4 PRB set or MPDCCH of aggregation level 8
of 2 PRB set although the base station has transmitted the MPDCCH
using 24 ECCEs, the MTC terminal transmits an ACK/NACK, using a
PUCCH resource to be identified from N_pucch corresponding to
aggregation level 16 of 4 PRB set or aggregation level 8 of 2 PRB
set.
[0142] For example, in FIG. 11, when recognizing that the MTC
terminal has received MPDCCH of aggregation level 16 of 4 PRB set,
the MTC terminal transmits an ACK/NACK using a PUCCH resource
(PUCCH set (0)) to be identified using N_pucch, 0 configured for 4
PRB set, and when recognizing that the MTC terminal has received
MPDCCH of aggregation level 8 of 2 PRB set, the MTC terminal
transmits an ACK/NACK using a PUCCH resource (PUCCH set (1)) to be
identified using N_pucch, 1 configured for 2 PRB set.
[0143] More specifically, in FIG. 11, there is a possibility that
the MTC terminal cannot transmits an ACK/NACK, using the PUCCH
resource corresponding to 24 ECCEs, which has been originally
planned by the base station. Meanwhile, there is a possibility that
the base station attempts to receive an ACK/NACK, using the
originally planned PUCCH resource corresponding to 24 ECCEs, and
erroneously recognizes an ACK/NACK. Moreover, there is a
possibility that transmission of an ACK/NACK, using a not planned
PUCCH resource from the MTC terminal provides interference to a
signal transmitted by another terminal.
[0144] Note that, in Option 1 (Frequency first), MPDCCH of 24 ECCEs
is mapped over 4 PRB set and 2 PRB set in units of OFDM symbols,
and since mapping of MPDCCH to the REs differs from MPDCCH of
aggregation level 16 of 4 PRB set or MPDCCH of aggregation level 8
of 2 PRB set, the problems relating to the above-mentioned
erroneous recognition do not occur.
[0145] In the present embodiment, a PUCCH resource identifying
method capable of avoiding the erroneous recognition will be
described.
[0146] A base station and a terminal according to Embodiment 3 have
basic configurations common to base station 100 and terminal 200
according to Embodiment 1, so that a description will be given
while FIGS. 6 and 7 are incorporated herein.
[0147] Hereinafter, Operation Examples 4 to 6 according to the
present embodiment will be described.
Operation Example 4
[0148] In Operation Example 4, when detecting MPDCCH of 24 ECCEs,
terminal 200 (MTC terminal) identifies a PUCCH resource, using
N_pucch, q configured for PRB set q to which MPDCCH of 24 ECCEs is
mapped first among a plurality of PRB sets in Narrowband. For
example, when MPDCCH of 24 ECCEs is mapped to PRB set 0, first and
then is mapped to PRB set 1, terminal 200, when detecting 24 ECCEs
of MPDCCH, identifies a PUCCH resource using N_pucch, 0 configured
for PRB set 0.
[0149] Accordingly, even in a case where terminal 200 erroneously
recognizes the MPDCCH transmitted from base station 100, using 24
ECCEs, as MPDCCH of the maximum aggregation level of PRB set 0,
terminal 200 can transmit an ACK/NACK using the PUCCH resource
secured for MPDCCH of 24 ECCEs. Therefore, it is possible for
terminal 200 to avoid erroneously selecting a PUCCH resource when
erroneous recognition 1 occurs.
[0150] Furthermore, the number of PRB pairs to which PRB set 0 in
which MPDCCH is mapped first is assigned may be greater than the
number of PRB pairs to which PRB set 1 in which MPDCCH is mapped
later is assigned. For example, PRB set 0 is set to 4 PRB set, and
PRB set 1 may be set to 2 PRB set. In this manner, the probability
of occurrence of erroneous recognition 2 can be lowered. This is
because in order for an MTC terminal to receive MPDCCH of 24 ECCEs
as aggregation level 8, even higher reception quality than that of
reception as aggregation level 16 is required, so that the
probability of occurrence of erroneous recognition of 24 ECCEs as
aggregation level 8 is lower than the probability of occurrence of
erroneous recognition of 24 ECCEs as aggregation level 16. Thus,
when PRB set 0 is set to 4 PRB set, and PRB set 1 is set to 2 PRB
set, the probability of occurrence of erroneous recognition 2 can
be lowered while erroneous selection of a PUCCH resource caused by
erroneous recognition 1 is avoided, by identifying a PUCCH resource
using N_pucch,0 configured for PRB set 0, when terminal 200 detects
MPDCCH of 24 ECCEs.
[0151] Moreover, according to the present embodiment, base station
100 and terminal 200 identify a PUCCH resource, using offset value
N_pucch configured for a PRB set to which MPDCCH is mapped, first.
Thus, as in Embodiment 1, base station 100 and terminal 200 can
identify, without addition of new signaling, the PUCCH resource
corresponding to MPDCCH mapped over a plurality of PRB sets as with
24 ECCEs. That is, the PUCCH resource of the case where one MPDCCH
is mapped to all 6 PRB pairs in Narrowband can be efficiently
identified.
Operation Example 5
[0152] In Operation Example 5, in order to avoid erroneous
selection of a PUCCH resource caused by erroneous recognition 2,
when detecting MPDCCH as the maximum aggregation level of a PRB
set, terminal 200 (MTC terminal) identifies a PUCCH resource, using
N_pucch, 0, in addition to the operations in Operation Example
4.
[0153] For example, when detecting MPDCCH with the maximum
aggregation level of PRB set 1, terminal 200 identifies the PUCCH
resource, using N_pucch,0, and when detecting MPDCCH with another
aggregation level of PRB set 1, terminal 200 identifies the PUCCH
resource, using N_pucch, configured for PRB set 1,
[0154] With this configuration, terminal 200 identifies a PUCCH
resource, using N_pucch, 0 for all three cases where MPDCCH is
detected with 24 ECCEs, where MPDCCH is detected with the maximum
aggregation level of PRB set 0, and where MPDCCH is detected with
the maximum aggregation level of PRB set 1.
[0155] Therefore, even when terminal 200 erroneously detects the
aggregation level of received MPDCCH, the PUCCH resource to be used
for transmission of an ACK/NACK signal becomes the same resource as
the resource of a case where no erroneous detection occurs. Thus,
erroneous selection of a PUCCH resource caused by erroneous
recognition 1 and erroneous recognition 2 can be avoided.
[0156] Note that, when base station 100 transmits MPDCCH directed
to a certain MTC terminal with the maximum aggregation level of PRB
set 1, and also transmits MPDCCH directed to another MTC terminal
with ECCE #0 of PRB set 0, there arises a problem in that PUCCH
resources corresponding to the MPDCCHs collide with each other.
This collision, however, can be avoided by ARO.
[0157] Moreover, in PRB set 1, only when an MTC terminal detects
MPDCCH with the maximum aggregation level, N_pucch, 0 is used, and
when an MTC terminal detects MPDCCH with another aggregation level,
N_pucch, 1 is used. Accordingly, with an aggregation level other
than the maximum aggregation level of PRB set 1, even when base
station 100 transmits MPDCCH including ECCE #0, the probability of
collision with a PUCCH resource of PRB set 0 does not change as
compared with a case where Operation Example 5 is not applied.
Operation Example 6
[0158] In Operation Example 6, in order to avoid erroneous
recognition 2, when mapping MPDCCH of 24 ECCEs, base station 100
differs the mapping order to REs from mapping to REs with the
maximum aggregation level of PRB set 1. Changing the mapping order
to the REs of MPDCCH makes it possible to avoid the occurrence of
erroneous detection as the maximum aggregation level of PRB set 1
in terminal 200 (MTC terminal) when MPDCCH of 24 ECCEs is
transmitted.
[0159] Hereinafter, a specific example of an MPDCCH mapping method
to REs will be described. Note that, in the following description,
MPDCCH is assigned in the order of PRB set 0 and PRB set 1 when
MPDCCH is assigned to 24 ECCEs. Moreover, PRB set 0 is set to 4 PRB
set and PRB set 1 is set to 2 PRB set.
[0160] Moreover, when MPDCCH is transmitted with the maximum
aggregation level of PRB set 1 (2 PRB set, herein), as in the case
of EPDCCH, within PRB set 1 (2 PRB set), MPDCCH is mapped from an
OFDM symbol with a low OFDM symbol number in ascending order of
frequency while vertically crossing over PRB pairs, and then moves
to the next OFDM symbol and is mapped in ascending order of
frequency while vertically crossing over PRB pairs, likewise.
Example 1: Mirroring
[0161] In Mirroring, as illustrated in FIG. 12A, when MPDCCH of 24
ECCEs is mapped, within PRB set 1 (2 PRB set), MPDCCH is mapped
from an OFDM symbol with a low OFDM symbol number in descending
order of frequency while vertically crossing over PRB pairs, and
then moves to the next OFDM symbol and is mapped in descending
order of frequency while vertically crossing over PRB pairs,
likewise. More specifically, in Mirroring, the mapping order of
MPDCCH in the frequency direction on each OFDM symbol is inverted
between the case of 24 ECCEs and the case of the maximum
aggregation level of PRB set 1.
[0162] Therefore, since the mapping order of MPDCCH differs within
PRB set 1 between the case where MPDCCH of 24 ECCEs is mapped and
the case where MPDCCH of the maximum aggregation level of PRB set 1
is mapped, it is made possible to avoid erroneous detection of an
aggregation level in an MTC terminal.
Example 2: PRB Pair Shifting
[0163] In PRB pair shifting, when MPDCCH of 24 ECCEs is mapped,
within PRB set 1 (2 PRB set), MPDCCH is mapped while the PRB pair
number is shifted. For example, in FIG. 12B, since 2 PRB set is
assigned to PRB pair #0 and PRB pair #1, for MPDCCH of 24 ECCEs,
mapping of MPDCCH of 24 ECCEs is switched between PRB pair #0 and
PRB pair #1 with respect to the case of the maximum aggregation
level of PRB set 1.
[0164] Accordingly, since the mapping order of MPDCCH within PRB
set 1 differs between the case where MPDCCH of 24 ECCEs is mapped
and the case where MPDCCH of the maximum aggregation level of PRB
set 1 is mapped, it is made possible to avoid erroneous detection
of an aggregation level in an MTC terminal.
Example 3: OFDM Symbol Shifting
[0165] In OFDM symbol shifting, when MPDCCH of 24 ECCEs is mapped,
within PRB set 1 (2 PRB set), MPDCCH is mapped while the OFDM
symbol number is shifted. For example, FIG. 12C illustrates an
example in which the OFDM symbol number is shifted by three
numbers. That is, within PRB set 1 (2 PRB set), MPDCCH is mapped
from OFDM symbol #3 in ascending order of frequency while
vertically crossing over PRB pairs, and then moves to the next OFDM
symbol and is mapped in ascending order of frequency while
vertically crossing over PRB pairs, likewise. Then, when the OFDM
symbol to which MPDCCH is mapped becomes the last OFDM symbol,
MPDCCH moves to the top OFDM symbol #0 and moves down to OFDM
symbol #2.
[0166] Accordingly, since the mapping order of MPDCCH within PRB
set 1 differs between the case where MPDCCH of 24 ECCEs is mapped
and the case where MPDCCH of the maximum aggregation level of PRB
set 1 is mapped, it is made possible to avoid erroneous detection
of an aggregation level in an MTC terminal.
[0167] The specific example of the MPDCCH mapping method to REs has
been described, thus far.
[0168] As described above, according to the present embodiment,
even in a case where terminal 200 erroneously detects the
aggregation level of MPDCCH, the PUCCH resource identical to the
PUCCH resource of the case where no erroneous detection has
occurred can be identified, or terminal 200 can be prevented from
erroneously detecting an aggregation level of MPDCCH. Thus, it is
made possible to avoid erroneous detection of an ACK/NACK signal in
base station 100. Moreover, transmission of an ACK/NACK using a
correct PUCCH resource from terminal 200 makes it possible to avoid
giving interference to a signal transmitted from another
terminal.
[0169] Note that, in the operation examples described above, a
description has been given of a case where MPDCCH of 24 ECCEs is
assigned in order of PRB set 0 and PRB set 1, but MPDCCH of 24
ECCEs may be assigned in order of PRB set 1 and PRB set 0.
[0170] Each embodiment of the present disclosure has been
described, thus far.
[0171] Note that, in Embodiments 1 and 2, a description has been
given with the example in which 4 PRB set and 2 PRB set are
assigned to non-overlapping PRB pairs in Narrowband. However, there
may be a case where 4 PRB set and 2 PRB set are assigned to
overlapping PRB pairs. FIGS. 13A and 13B illustrate an example in
which 4 PRB set is assigned to PRB pairs #2, #3, #4, and #5, and 2
PRB set is assigned to PRB pairs #2 and #3 which are overlapping
PRB pairs. Note that, in FIGS. 13A and 13B, an assumption is made
that Option 1 (Frequency first) is used for MPDCCH mapping of 24
ECCEs. More specifically, a symbol sequence of MPDCCH of 24 ECCEs
in Narrowband is mapped from an OFDM symbol with a low OFDM symbol
number in ascending order of frequency while vertically crossing
over PRB pairs, and then moves to the next OFDM symbol and is
mapped in ascending order of frequency while vertically crossing
over PRB pairs, likewise. Even in the case of mapping in which 4
PRB set and 2 PRB set overlap with each other, Operation Example 2
of Embodiment 1 and Operation Example 3 of Embodiment 2 can be
applied. For example, in Operation Example 2, when an MTC terminal
detects MPDCCH of 24 ECCEs, a PUCCH resource may be identified
using N_pucch, 0. Moreover, in Operation Example 3, when an MTC
terminal detects MPDCCH of 24 ECCEs, a PUCCH resource may be
identified using N_pucch configured in common to a plurality of PRB
sets.
[0172] Although a description has been given with an example of a
case where an aspect of the present disclosure is formed by
hardware in each of the embodiments, the present disclosure can be
realized by software in cooperation with hardware.
[0173] Each functional block used in the description of each
embodiment described above can be partly or entirely realized by an
LSI such as an integrated circuit, and each process described in
each embodiment may be controlled partly or entirely by the same
LSI or a combination of LSIs. The LSI may be individually formed as
chips, or one chip may be formed so as to include a part or all of
the functional blocks. The LSI may include a data input and output
coupled thereto. The LSI herein may be referred to as an IC, a
system LSI, a super LSI, or an ultra LSI depending on a difference
in the degree of integration.
[0174] Moreover, the technique of implementing an integrated
circuit is not limited to the LSI and may be realized by using a
dedicated circuit, a general-purpose processor, or a
special-purpose processor. In addition, a Field Programmable Gate
Array (FPGA) that can be programmed after the manufacture of the
LSI or a reconfigurable processor in which the connections and the
settings of circuit cells disposed inside the LSI can be
reconfigured may be used.
[0175] Moreover, if future integrated circuit technology replaces
LSIs as a result of the advancement of semiconductor technology or
other derivative technology, the functional blocks could be
integrated using the future integrated circuit technology.
Biotechnology can also be applied.
[0176] A base station of the present disclosure includes: a signal
assignment section that assigns a downlink control signal to a
downlink resource, the downlink control signal including resource
allocation information on Physical Downlink Shared Channel (PDSCH):
an identifying section that identifies a Physical Uplink Control
Channel (PUCCH) resource based on the downlink resource to which
the downlink control signal has been assigned, the PUCCH resource
being a resource to which an ACK/NACK signal for the PDSCH is
assigned; and a signal separating section that separates the
ACK/NACK signal included in the identified PUCCH resource from a
received signal from a terminal to which the downlink control
signal has been transmitted, in which the downlink resource is
composed of a plurality of PRB pairs, and any of a first PRB set
and a second PRB set is assigned to each of the plurality of PRB
pairs, and in a case where the downlink control signal is mapped
over the first PRB set and the second PRB set, the identifying
section identifies the PUCCH resource, using an offset value
configured for any of the first PRB set and the second PRB set.
[0177] In the base station of the present disclosure, mutually
different offset values are configured for the first PRB set and
the second PRB set, respectively, and in a case where the downlink
control signal is mapped over the first PRB set and the second PRB
set, the identifying section identifies the PUCCH resource, using
an offset value configured for a PRB set assigned to a PRB pair
having a minimum PRB number, among the first PRB set and the second
PRB set.
[0178] In the base station of the present disclosure, mutually
different offset values are configured for the first PRB set and
the second PRB set, respectively, and in a case where the downlink
control signal is mapped over the first PRB set and the second PRB
set, the identifying section identifies the PUCCH resource, using
an offset value configured for a PRB set having a smaller PRB set
number among the first PRB set and the second PRB set.
[0179] In the base station of the present disclosure, mutually
different offset values are configured for the first PRB set and
the second PRB set, respectively, and in a case where the downlink
control signal is mapped over the first PRB set and the second PRB
set, the identifying section identifies the PUCCH resource, using
an offset value having a smaller value among the offset values
configured for the first PRB set and the second PRB set.
[0180] In the base station of the present disclosure, a common
offset value is configured for the first PRB set and the second PRB
set, and the identifying section identifies the PUCCH resource,
using the common offset value.
[0181] In the base station of the present disclosure, mutually
different offset values are configured for the first PRB set and
the second PRB set, respectively, and in a case where the downlink
control signal is mapped over the first PRB set and the second PRB
set, the identifying section identifies the PUCCH resource, using
an offset value configured for a PRB set in which the downlink
control signal is mapped first, among the first PRB set and the
second PRB set.
[0182] In the base station of the present disclosure, the number of
PRB pairs to which the PRB set in which the downlink control signal
is mapped first is assigned is greater than the number of PRB pairs
to which a PRB set in which the downlink control signal is mapped
later is assigned.
[0183] A terminal of the present disclosure includes: a receiving
section that receives a downlink control signal including resource
allocation information on Physical Downlink Shared Channel (PDSCH);
and an identifying section that identifies a Physical Uplink
Control Channel (PUCCH) resource based on a downlink resource to
which the downlink control signal has been assigned, the PUCCH
resource being a resource to which an ACK/NACK signal for the PDSCH
is assigned; and a signal assignment section that assigns the
ACK/NACK signal to the identified PUCCH resource, in which the
downlink resource is composed of a plurality of PRB pairs, and any
of a first PRB set and a second PRB set is assigned to each of the
plurality of PRB pairs, and in a case where the downlink control
signal is mapped over the first PRB set and the second PRB set, the
identifying section identifies the PUCCH resource, using an offset
value configured for any of the first PRB set and the second PRB
set.
[0184] A communication method of the present disclosure includes:
assigning a downlink control signal to a downlink resource, the
downlink control signal including resource allocation information
on Physical Downlink Shared Channel (PDSCH): identifying a Physical
Uplink Control Channel (PUCCH) resource based on the downlink
resource to which the downlink control signal has been assigned,
the PUCCH resource being a resource to which an ACK/NACK signal for
the PDSCH is assigned; and separating the ACK/NACK signal included
in the identified PUCCH resource from a received signal from a
terminal to which the downlink control signal has been transmitted,
in which the downlink resource is composed of a plurality of PRB
pairs, and any of a first PRB set and a second PRB set is assigned
to each of the plurality of PRB pairs, and in a case where the
downlink control signal is mapped over the first PRB set and the
second PRB set, the PUCCH resource is identified using an offset
value configured for any of the first PRB set and the second PRB
set.
[0185] A communication method of the present disclosure includes:
receiving a downlink control signal including resource allocation
information on Physical Downlink Shared Channel (PDSCH);
identifying a Physical Uplink Control Channel (PUCCH) resource
based on a downlink resource to which the downlink control signal
has been assigned, the PUCCH resource being a resource to which an
ACK/NACK signal for the PDSCH is assigned; and assigning the
ACK/NACK signal to the identified PUCCH resource, in which the
downlink resource is composed of a plurality of PRB pairs, and any
of a first PRB set and a second PRB set is assigned to each of the
plurality of PRB pairs, and in a case where the downlink control
signal is mapped over the first PRB set and the second PRB set, the
PUCCH resource is identified using an offset value configured for
any of the first PRB set and the second PRB set.
INDUSTRIAL APPLICABILITY
[0186] An aspect of the present disclosure is useful for mobile
communication systems.
REFERENCE SIGNS LIST
[0187] 100 Base station [0188] 101 Aggregation level configuration
section [0189] 102 MPDCCH generation section [0190] 103, 209 Error
correction coding section [0191] 104, 210 Modulation section [0192]
105, 211 Signal assignment section [0193] 106, 212 Transmitting
section [0194] 107, 201 Receiving section [0195] 108, 208 PUCCH
resource identifying section [0196] 109, 202 Signal separating
section [0197] 110 PUCCH receiving section [0198] 111, 203
Demodulation section [0199] 112, 204 Error correction decoding
section [0200] 200 Terminal [0201] 205 Error determination section
[0202] 206 ACK/NACK generation section [0203] 207 MPDCCH receiving
section
* * * * *